CODASYL DBTG Database Recovery   Oracle Tips by Burleson Consulting

High Performance Data Warehousing

The CODASYL Generation Of Database Management 

Many of the problems associated with flat-file systems were partially addressed with the introduction of the IMS database product by IBM, but there remained no published standard for commercial database systems. In the late 1970s, an ANSI committee created the Committee on Development of Applied Symbolic Languages (CODASYL). The CODASYL committee formed a database task group (the DBTG) to address database standards and required some of the leading database theoreticians to participate in the development of the standard. The CODASYL DBTG was commissioned to develop a set of rules, or standards, for database management systems. The CODASYL DBTG developed what is called the Network Model for databases. Among other things, the CODASYL DBTG decided:

* A framework for a Metadata Dictionary would be created. The data dictionary was designed to store all metadata, including information about the database entities, relationships between entities, and information about how programs use the database.

* To describe a standard architecture for network database systems. This architecture was based on a combination of the BDAM (direct access) and linked-list data structures.
A method for separation of the logical data structure of the data from the physical access methods. For example, a programmer could state obtain calc customer where cust-id=’IBM’, without having to worry about where the record was physically stored on the disk.

* A process for database recovery. Databases would manage record locks, preventing information overlaying, and databases could be rolled-forward or rolled-back, thereby insuring data integrity.

Figure 1.6 The use of database recovery mechanisms.

The CODASYL model became the framework for new commercial database systems, such as the IDMS database from Cullinane corporation (Now Computer Associates) and the MDBS2 database.

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This is an excerpt from "High Performance Data Warehousing", copyright 1997.

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